Enlargement of the prostate gland (known as benign prostatic hyperplasia or hypertrophy—“BPH”) is a common ailment in older men. BPH affects 40% of men in their 50s and 90% of men in their 80s. The enlargement of the prostate is a form of benign tumor or adenoma. FIG. 1 illustrates a simplified view of the anatomy and location of the prostate 3, 4. The urethra 1 passes upwards through the external urethral sphincter 2, through the prostate 3, 4 (surrounding the urethra), and into the bladder 5. The prostate 3, 4 comprises three lobes: two major lobes 3, 4 and a median lobe. The median lobe is located generally behind the major lobes 3, 4.
As the prostate becomes enlarged, it may compress the urethra and cause one or more of the following symptoms to occur: more frequent urination, weak urine stream, inability to delay urination, difficulty starting and stopping urination, incomplete emptying of the bladder, loss of bladder control, and painful or bloody urination.
If symptoms are mild and do not affect quality of life, treatment may not be performed. If diagnosed with BPH but not pursuing treatment options, men typically receive regular checkups and report increased BPH symptoms to the physician. If symptoms occur and cause discomfort, affect activities of daily living, or endanger health, drug treatment or surgery may be recommended. Treatment options for BPH include lifestyle changes (such as adjusting fluid intake), herbal remedies, drug therapy, non-surgical procedures, and surgical procedures. The goals of treatment are generally to improve urinary flow and decrease symptoms associated with BPH. Treatment may delay or prevent the progression of BPH.
Drugs may be used to relieve the common urinary symptoms associated with BPH by either reducing the size of the prostate gland or by slowing the growth of the prostate. Common drug classes used to treat urinary symptoms include alpha blockers, such as doxazosin or tamsulosin, and 5-alpha reductase inhibitors, such as finasteride or dutasteride. The medications may have deleterious side effects such as decreased libido, impotence, retrograde ejaculation, fatigue, dizziness, headache, and decreased blood pressure. If drug therapy does not provide adequate relief of symptoms, surgery may be needed to help correct the prostate gland overgrowth. Further, if more severe symptoms of BPH present, such as recurrent urinary retention, recurrent blood in the urine, recurrent urinary tract infections or bladder stones, drug therapy should not be initiated. Generally, upon presentation of these symptoms, surgery is indicated.
Surgical treatments of BPH may or may not be minimally invasive. For the surgical methods, access to the prostate may be via the urethra, the perineum, or other route.
Non-minimally invasive surgical treatments include Trans Urethral Resection of the Prostate (TURP). Conducted in an operating room under general or spinal anesthetic, a probe is passed through the urethra which scrapes away prostate tissue causing the blockage. Side effects may include retrograde ejaculation, impotence, and a repeat of the procedure if the blockage regrows. U.S. Pat. No. 6,491,672, herein incorporated by reference, discloses one surgery option for treating BPH.
Minimally invasive surgical treatments usually offer the incentives of less pain, faster recovery, lower costs, and use of local anesthesia and a mild sedative. In general, minimally invasive surgical treatments destroy prostate tissue through one of various mechanisms. The destroyed prostate tissue may be reabsorbed by the body and/or discharged into the urine over a period of time. Minimally-invasive surgical treatment options include generation of heat, freezing, chemical means, and ultrasound to destroy prostate tissue. Care must be taken to avoid damaging sensitive areas adjacent the prostate such as nerves controlling sexual functions or the rectal wall.
Various types of laser treatment of BPH exist including laser prostatectomy, interstitial laser coagulation, photosensitive vaporization of the prostate, Holmium laser ablation of the prostate, and Holmium laser enucleation of the prostate (HoLEP). Laser prostatectomy uses a transurethral laser device to cut or vaporize obstructions. Interstitial Laser Coagulation uses a cystoscope through which a fiberoptic probe is directly introduced into the prostate. A small laser fiber is inserted into the prostate through the device inserted in the urethra. Laser energy heats a selected area and the probe may be moved several times to treat all areas of obstruction. Photosensitive vaporization of the prostate (PVP) uses a laser delivered through an endoscope inserted into the urethra. The high-energy laser vaporizes excess prostate tissue and seals the treated area.
For microwave treatment of BPH, a microwave antenna is inserted transurethrally into the prostate. Various forms of microwave treatment may include a cooling means for minimizing patient discomfort and to protect adjacent urethral tissue from damage. Further means may be used to dilate the urethra.
Heat for treatment of BPH may be generated, for example, via laser beams, microwaves, radiofrequency current, or direct current. Other heat application techniques exist for treating BPH including transurethral vaporization of the prostate (TUVP) wherein heat is applied directly to the prostate with a grooved roller bar that vaporizes tissue and water-induced thermotherapy (WIT) to destroy obstructive tissue wherein hot water flows through a transurethrally-placed balloon. U.S. Pat. Nos. 5,928,225 and 6,640,139, herein incorporated by reference in their entirety, further disclose treatment methods using heat.
Non-thermal treatments of BPH include injection of ethanol (see, for example, U.S. Pat. No. 7,015,253) or direct current ablation (see, for example, U.S. Pat. Nos. 7,079,890; 6,733,485; and 6,901,294).
Transurethral ethanol ablation of the prostate (TEAP) may be used to treat BPH and typically uses a cystoscope with a curved needle to inject ethanol in various doses.
High intensity focused ultrasound (HIFU) may be used to treat BPH and noninvasively focuses ultrasound waves to heat and destroy targeted prostate tissue.
Various radiofrequency current treatment methods of BPH have been developed. Some methods are shown and described in U.S. Pat. Nos. 6,106,521; 6,638,275; and 6,016,452, all herein incorporated by reference in their entireties. In one treatment method, transurethral needle ablation, a small needle is inserted into the prostate from the urethra. Radio frequency (RF) energy is applied to the needle to generate heat in specific areas of the prostate. RF frequency based ablation of tissue is done via thermal treatment. Typically, treatment is done until a certain temperature is reached and is then discontinued. An assumption is made that sufficient ablation has occurred on the basis of the reached temperature.
As may be appreciated, many of these BPH treatment methods include transurethral access. Transurethral access may involve catheter-based electrodes within the prostatic urethra (see, for example, U.S. Pat. Nos. 6,517,534 and 5,529,574) or electrodes designed to puncture the urethra and dwell inside the prostate (see, for example, U.S. Pat. Nos. 6,638,275; 6,016,452; 5,800,378; and 5,536,240), transurethral access including balloons for positioning and stabilizing the electrodes (see, for example, U.S. Pat. Nos. 6,517,534 and 7,066,905), transurethral access including means for puncturing the urethral wall (see, for example, U.S. Pat. No. 5,385,544), and transurethral access including means for more accurately placing the electrodes (see, for example, U.S. Pat. No. 6,638,275).
Accordingly, a need exists in the art for a minimally invasive low power, non-thermal method of treating tissue via direct current ablation.